JP5942043B2 - Imaging apparatus and focus control method - Google Patents

Description

  The present invention relates to an imaging apparatus and a focus control method.

  In recent years, with the increase in the resolution of solid-state image sensors such as CCD (Charge Coupled Device) image sensors and CMOS (Complementary Metal Oxide Semiconductor) image sensors, mobile phones such as digital still cameras, digital video cameras, and smartphones, PDA (Personal Digital). Demand for information equipment having a photographing function such as an assistant (mobile information terminal) is rapidly increasing. Note that an information device having the above imaging function is referred to as an imaging device.

  In these imaging apparatuses, a contrast AF (Auto Focus) method or a phase difference AF method is employed as a focusing control method for focusing on a main subject.

  There is also known an imaging apparatus having a mode in which lens driving is made to follow a moving subject. For example, in Patent Document 1, a future image plane position is predicted from information on image plane positions obtained a plurality of times in the past, and the predicted image plane position and the light receiving surface of the image sensor coincide with each other at the next exposure. Describes an imaging device that drives a lens.

Japanese Patent Laid-Open No. 2001-21794

  The distance from the object to the principal point of the lens (subject distance) is b, the distance from the principal point of the lens to the imaging plane of the object (image plane distance) is a, and the distance between the lens principal point and the focal point of the lens When (focal length) is f, (1 / a) + (1 / b) = (1 / f) (1) holds.

  Multiplying both sides of equation (1) by abf yields af + bf = ab (2).

  Here, assuming that the amount of deviation between the focal point of the lens and the imaging plane is the amount of image deviation a ′, the relationship a = f + a ′ (3) holds.

Substituting equation (3) into equation (2) and rearranging results in a ′ (f−b) = − f ² (4).

In Formula (4), assuming that the subject distance is sufficiently large, when (f−b) is approximated by −b, a ′ = f ² / b (5).

Substituting equation (3) into equation (5) and rearranging results in a = (f ² / b) + f (6).

  Thus, it can be seen from equation (6) that the image plane distance a is inversely related to the subject distance. For this reason, when a subject moving in the perspective direction at a constant speed is observed on the imaging plane of the subject, the intervals of the image plane distance a for each subject position are not uniform. Therefore, in order to accurately predict the image plane distance a, it is necessary to use a polynomial prediction formula as described in Patent Document 1, but this increases the amount of calculation.

  The present invention has been made in view of the above circumstances, and provides an imaging apparatus capable of improving moving object prediction accuracy while reducing the amount of calculation in moving object prediction that is used when focusing on a moving subject. For the purpose.

  The imaging device of the present invention is an imaging device having an imaging device that images a subject through an imaging optical system including a focus lens, and the imaging device has a pair of light beams that have passed through different parts of the pupil region of the imaging optical system. A first signal detection unit that detects a signal corresponding to one of the pair of light beams and a second signal detection unit that detects a signal corresponding to the other of the pair of light beams, and drives the focus lens to A focus control unit that performs focusing control to focus on the image, and a correlation calculation between the detection signal of the first signal detection unit and the detection signal of the second signal detection unit obtained by imaging performed by the imaging device A focus lens position generation unit that obtains a focus lens position that is a position of the focus lens where an imaging surface on which a main subject is imaged and a light receiving surface of the image sensor coincide with each other based on the result; A subject distance conversion unit that converts the focus lens position obtained by the focus lens position generation unit into a subject distance that is a distance between a main subject and the focus lens, and a time series generated by the subject distance conversion unit. Generated by the subject distance prediction unit for predicting the subject distance in the imaging performed after the last imaging of the plurality of imagings, and the focus lens position generation unit, from the subject distances corresponding to the plurality of imagings. A focus lens position predicting unit that predicts the focus lens position in the imaging performed after the last imaging of the plurality of imaging from the focus lens position corresponding to each of a plurality of imagings consecutive in time series; and the focus The focus lens position generated by the lens position generator A maximum error information acquisition unit that acquires error information, and the focus control unit is generated by the focus lens position generation unit as focus control performed before imaging performed after the last imaging. And driving the focus lens in accordance with the focus lens position predicted by the lens position prediction unit based on the focus lens position corresponding to each of a plurality of continuous images in time series and the information on the maximum error. And the second focus control for driving the focus lens in accordance with the subject distance predicted by the subject distance prediction unit.

  The focus control method of the present invention is a focus control method in an image pickup apparatus having an image pickup device that picks up an image of a subject through an image pickup optical system including a focus lens, and the image pickup device has different pupil regions of the image pickup optical system. A first signal detection unit that detects a signal corresponding to one of the pair of light beams that has passed through the portion; and a second signal detection unit that detects a signal corresponding to the other of the pair of light beams. Based on the result of the correlation calculation of the detection signal of the first signal detection unit and the detection signal of the second signal detection unit obtained by the imaging performed by the imaging, the imaging plane on which the main subject is imaged and the imaging A focus lens position generation step for obtaining a focus lens position, which is the position of the focus lens that matches the light receiving surface of the element, and a focus lens position obtained in the focus lens position generation step. A subject distance conversion step for converting the lens position into a subject distance that is a distance between the main subject and the focus lens, and the subject distance corresponding to each of a plurality of continuous imagings generated in the subject distance conversion step. To a subject distance prediction step for predicting a subject distance in an imaging performed after the last imaging of the plurality of imaging, and a plurality of time-sequential imagings generated in the focus lens position generation step. A focus lens position predicting step for predicting the focus lens position in the imaging performed after the last imaging of the plurality of imaging from the focus lens position, and a maximum for the focus lens position generated in the focus lens position generating step Maximum error information acquisition step for acquiring error information And the focus lens position corresponding to each of a plurality of time-sequentially generated images generated in the focus lens position generation step as the focus control performed for imaging performed after the last imaging, and Based on the maximum error information, the first focus control for driving the focus lens according to the focus lens position predicted in the focus lens position prediction step, and the focus according to the subject distance predicted in the subject distance prediction step. A focus control step of selecting any one of the second focus controls for driving the lens and executing the selected focus control before the imaging.

  ADVANTAGE OF THE INVENTION According to this invention, the imaging device which can improve a moving body prediction precision can be provided, reducing the amount of calculations in the moving body prediction used when continuing to focus on the to-be-moved subject.

1 is a diagram illustrating a schematic configuration of a digital camera as an example of an imaging apparatus for describing an embodiment of the present invention. FIG. 2 is a schematic plan view showing an overall configuration of a solid-state image sensor 5 mounted on the digital camera shown in FIG. 1. FIG. 3 is a partially enlarged view of one AF area 53 shown in FIG. 2. FIG. 4 is a diagram showing only a phase difference detection pixel 52 shown in FIG. 3. It is a figure for demonstrating the calculation method of the largest error with respect to a focus lens position. 2 is a flowchart for explaining an operation in a continuous shooting mode of the digital camera shown in FIG. 1. It is a figure which shows the relationship between a to-be-photographed object distance and the focus lens position in an in-focus state. 10 is a flowchart for explaining a modification of a method for calculating an error that may occur in the subject distance. It is a figure for demonstrating step S22, S23 in the operation | movement of FIG. It is a figure explaining a smart phone as an imaging device. It is an internal block diagram of the smart phone of FIG.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a diagram showing a schematic configuration of a digital camera as an example of an imaging apparatus for explaining an embodiment of the present invention.

  The digital camera shown in FIG. 1 includes a lens device having an imaging lens 1 including a focus lens for zooming, a zoom lens, and the like, and a diaphragm 2. The lens device constitutes an imaging optical system. The lens device is fixed to the camera body. The imaging lens 1 only needs to include at least a focus lens. Alternatively, a single focus lens that performs focus adjustment by moving the entire lens system may be used.

  The camera body includes a solid-state imaging device 5 such as a CCD type or a CMOS type that images a subject through a lens device, and an analog signal processing unit that performs analog signal processing such as correlated double sampling processing connected to the output of the solid-state imaging device 5 6 and an A / D conversion circuit 7 for converting an analog signal output from the analog signal processing unit 6 into a digital signal. The analog signal processing unit 6 and the A / D conversion circuit 7 are controlled by the system control unit 11. The analog signal processing unit 6 and the A / D conversion circuit 7 may be built in the solid-state imaging device 5.

A system control unit 11 that performs overall control of the electrical control system of the digital camera controls the lens driving unit 8 to adjust the position of the focus lens included in the imaging lens 1 and performs focusing control to focus on the main subject. Or the position of the zoom lens included in the imaging lens 1 is adjusted. Further, the system control unit 11 adjusts the exposure amount by controlling the aperture amount of the aperture 2 via the aperture drive unit 9. The system control unit 11 functions as an in-focus control unit.

  In addition, the system control unit 11 drives the solid-state imaging device 5 via the imaging device driving unit 10 and outputs a subject image captured through the imaging lens 1 as a captured image signal. An instruction signal from the user is input to the system control unit 11 through the operation unit 14.

  Further, the electric control system of the digital camera includes an interpolation calculation and a gamma correction for the main memory 16, the memory control unit 15 connected to the main memory 16, and the captured image signal output from the A / D conversion circuit 7. A digital signal processing unit 17 that performs calculation, RGB / YC conversion processing, and the like to generate captured image data, a phase difference AF processing unit 19 that determines a focus position by a phase difference AF method, and a detachable recording medium 21 Are connected to the external memory control unit 20 and the display control unit 22 is connected to the display unit 23 mounted on the back of the camera.

  The memory control unit 15, the digital signal processing unit 17, the phase difference AF processing unit 19, the external memory control unit 20, and the display control unit 22 are connected to each other by a control bus 24 and a data bus 25. Controlled by command.

  FIG. 2 is a schematic plan view showing the overall configuration of the solid-state imaging device 5 mounted on the digital camera shown in FIG.

  The solid-state imaging device 5 has a light receiving surface 50 on which a large number of pixels arranged two-dimensionally in a row direction X and a column direction Y orthogonal thereto. In the light receiving surface 50, nine AF areas 53, which are areas to be focused, are provided in the example of FIG.

  The AF area 53 is an area including imaging pixels and phase difference detection pixels as pixels.

  Only the imaging pixels are arranged on the light receiving surface 50 excluding the AF area 53. The AF area 53 may be provided on the light receiving surface 50 without a gap.

  FIG. 3 is a partially enlarged view of one AF area 53 shown in FIG.

  In the AF area 53, the pixels 51 are two-dimensionally arranged. Each pixel 51 includes a photoelectric conversion unit such as a photodiode and a color filter formed above the photoelectric conversion unit.

  In FIG. 3, a pixel 51 (R pixel 51) including a color filter (R filter) that transmits red light is denoted by “R”, and a pixel 51 including a color filter (G filter) that transmits green light. The letter “G” is assigned to (G pixel 51), and the letter “B” is assigned to pixel 51 (B pixel 51) including a color filter (B filter) that transmits blue light. The color filter array is a Bayer array over the entire light receiving surface 50.

  In the AF area 53, a part of the G pixel 51 (the shaded pixel 51 in FIG. 3) is the phase difference detection pixel 52. In the example of FIG. 3, each G pixel 51 in an arbitrary pixel row among the pixel rows including the R pixel 51 and the G pixel 51, and the G pixel 51 of the same color closest to the G pixel 51 in the column direction Y. Are the phase difference detection pixels 52. Here, as shown in FIG. 3, one direction of the two-dimensional array is defined as an X direction or a row direction, and the other direction is defined as a Y direction or a column direction.

  FIG. 4 is a diagram showing only the phase difference detection pixels 52 shown in FIG.

  As shown in FIG. 4, the phase difference detection pixel 52 includes two types of pixels, a phase difference detection pixel 52A and a phase difference detection pixel 52B.

  The phase difference detection pixel 52A is a first signal detection unit that receives one of a pair of light beams that have passed through different portions of the pupil region of the imaging lens 1 and detects a signal corresponding to the amount of received light.

  The phase difference detection pixel 52B is a second signal detector that receives the other of the pair of light beams and detects a signal corresponding to the amount of received light.

  In the AF area 53, the plurality of pixels 51 other than the phase difference detection pixels 52A and 52B are imaging pixels, and the imaging pixels receive the pair of light beams that have passed through the imaging lens 1 and correspond to the amount of received light. Detects the detected signal.

  A light shielding film is provided above the photoelectric conversion unit of each pixel 51, and an opening that defines a light receiving area of the photoelectric conversion unit is formed in the light shielding film.

  The center of the opening of the imaging pixel 51 coincides with the center of the photoelectric conversion unit of the imaging pixel 51. In contrast, the center of the opening (outlined portion in FIG. 4) of the phase difference detection pixel 52A is eccentric to the right side with respect to the center of the photoelectric conversion unit of the phase difference detection pixel 52A. Further, the center of the opening (outlined portion in FIG. 4) of the phase difference detection pixel 52B is eccentric to the left with respect to the center of the photoelectric conversion unit of the phase difference detection pixel 52B. The right direction here is one direction of the X direction shown in FIG. 3, and the left direction is the other direction of the X direction.

  With this configuration, the pixel group including the phase difference detection pixels 52A in an arbitrary row, and the phase difference detection pixels 52B arranged at the same distance in one direction with respect to the phase difference detection pixels 52A of the pixel group. The phase difference in the row direction X in the image captured by each of these two pixel groups can be detected.

  The phase difference AF processing unit 19 shown in FIG. 1 reads out from the phase difference detection pixel 52A and the phase difference detection pixel 52B in one AF area 53 selected from among the nine AF areas 53 by a user operation or the like. Using the detection signal group, a phase difference that is a relative positional shift amount between the two images formed by the pair of light beams is calculated.

  Then, based on this phase difference, the phase difference AF processing unit 19 generates information on the position of the focus lens when the imaging surface of the main subject by the imaging lens 1 coincides with the light receiving surface of the solid-state imaging device 5. . The phase difference AF processing unit 19 functions as a focus lens position generation unit. Specifically, the phase difference AF processing unit 19 obtains a defocus amount from the phase difference, converts the defocus amount into a drive pulse number of a motor that drives the focus lens, and this drive pulse number is in a focused state. Information indicating the position of the focus lens for obtaining

  In this specification, for example, the closest end in the movable range of the focus lens is set as a reference position, and the distance (number of drive pulses) from this reference position is set as the position of the focus lens.

  It should be noted that the number of AF areas 53 is not limited to one, and a plurality of continuously arranged AF areas 53 may be selected.

  The phase difference calculated by the phase difference AF processing unit 19 cannot be obtained with an accuracy equal to or higher than the arrangement interval of the phase difference detection pixels 52A or the phase difference detection pixels 52B in the row direction X. In the example of FIG. 3, the phase difference detection pixels 52 </ b> A are arranged with one pixel therebetween, so that the phase difference can be detected in units of one pixel. However, a phase difference with a distance smaller than one pixel cannot be detected. For example, even when the image captured by the phase difference detection pixel 52A and the image captured by the phase difference detection pixel 52B are shifted by 0.5 pixels in the row direction X, the phase difference is detected as one pixel. Thus, an error of 0.5 pixels occurs.

  The phase difference calculated by the phase difference AF processing unit 19 is the F value of the imaging lens 1 (the focal length of the imaging lens 1 is the aperture of the imaging lens 1 (the aperture when the aperture 2 is opened), even when the same subject is imaged. 2), the size changes depending on the aperture value at the time of imaging, the zoom magnification at the time of imaging, the noise of the solid-state imaging device 5, and the like. Therefore, the magnitude of the error described above varies depending on the F value of the imaging lens 1, the aperture value at the time of imaging, the zoom magnification at the time of imaging, the noise of the solid-state imaging element 5, and the like.

  The digital camera shown in FIG. 1 stores information on the maximum error (hereinafter referred to as the maximum error) that can occur with respect to the focus lens position for obtaining the in-focus state generated by the phase difference AF processing unit 19 in the main memory 16. Pre-stored.

  As a method of obtaining the maximum error, a focus lens obtained from a phase difference obtained in each combination by changing the aperture value and the zoom magnification in every combination for an object with a known focus lens position in a focused state. There is a method of obtaining a difference between the largest value of the positions and the known focus lens position as a maximum error.

  Further, there is a method for obtaining the maximum error from the arrangement interval of the phase difference detection pixels 52 in the row direction X and the F value of the imaging lens 1.

  FIG. 5 is a diagram for explaining a method for obtaining the maximum error by calculation.

  As shown in FIG. 5, the distance between the imaging surface, which is the surface on which the main subject P is imaged by the imaging lens 1, and the light receiving surface of the solid-state imaging device 5 is x and is calculated by the phase difference AF processing unit 19. Let y be the phase difference, and θ be the incident angle of light incident from the main subject P onto the image plane.

  Since the F value of the imaging lens 1 has a relationship of F value = 2 / tan (θ), tan (θ) = 2 / (F value).

  The distance x is x = y / 2 tan (θ), and if tan (θ) = 2 / (F value) is substituted here, x = y * (F value) / 4.

  Here, as described above, since a value smaller than the arrangement interval of the phase difference detection pixels in the row direction X cannot be detected as the value of y, in the expression x = y * (F value) / 4, A value obtained by converting the value obtained by substituting the arrangement interval into the number of drive pulses is the maximum error. Thus, the maximum error can be calculated from the information on the arrangement interval of the phase difference detection pixels and the information on the F value of the imaging lens 1.

  Hereinafter, continuous shooting mode in which imaging processing for capturing an image (still image capturing) with the solid-state imaging device 5 in a state where the main subject is focused is continuously performed a plurality of times (hereinafter, K times are set). The operation of the digital camera will be described. Imaging refers to processing from the start of exposure of the solid-state imaging device 5 to reading of a captured image signal obtained by the exposure from the solid-state imaging device 5.

  When the continuous shooting mode is set, the system control unit 11 causes the solid-state imaging device 5 to start imaging for live view image display. Thereby, a series of processes of imaging by the solid-state imaging device 5, generation of captured image data from the captured image signal obtained by the imaging, and display of the live view image based on the captured image data on the display unit 23 are repeatedly performed. Is called.

  When there is an instruction to start continuous shooting by operating the shutter button included in the operation unit 14, the phase difference AF processing unit 19 selects the AF area 53 selected from the captured image signal obtained by imaging immediately before the instruction. The detection signals of the phase difference detection pixel 52A and the phase difference detection pixel 52B are acquired, and the correlation calculation between the detection signal groups of the phase difference detection pixel 52A and the phase difference detection pixel 52B is performed.

  The phase difference AF processing unit 19 obtains a phase difference from the result of the correlation calculation, calculates a focus lens position for obtaining a focused state from the phase difference, and associates the calculated focus lens position with the calculated time. And stored in the main memory 16 (step S1).

  Next, the system control unit 11 acquires information on the focus lens position calculated by the phase difference AF processing unit 19, performs focus control to move the focus lens to the focus lens position, and then performs the solid-state imaging device 5. Thus, the Nth frame of continuous shooting is taken (step S2). Note that the initial value of N is “1”.

  Captured image data is generated by the digital signal processing unit 17 from the captured image signal obtained by the imaging in step S <b> 2, and the captured image data is recorded on the recording medium 21.

  After step S2, if N = K (step S3: YES), the system control unit 11 ends the continuous shooting, and if N ≠ K (step S3: NO), the system control unit 11 proceeds to step S4. The phase difference AF processing unit 19 performs the processing.

  In step S4, the phase difference AF processing unit 19 calculates a focus lens position for obtaining an in-focus state using the detection signal of the phase difference detection pixel included in the captured image signal obtained by imaging in step S2. The calculated focus lens position is stored in the main memory 16 in association with the calculated time.

  After step S4, the system control unit 11 selects the focus lens position stored in the main memory 16 with the latest associated time (referred to as the focus lens position l1) and the next newest ( Focus lens position l2) is acquired from the main memory 16, and the acquired focus lens positions l1 and l2 are converted into subject distances (step S5). The system control unit 11 functions as a subject distance conversion unit.

  The focused state means that the light receiving surface of the solid-state imaging device 5 and the imaging surface of the imaging lens 1 coincide with each other, so that the focus lens position for obtaining the focused state is focused on the principal point of the imaging lens 1. This corresponds to the image plane distance a described above, which is the distance to the surface.

  Therefore, in step S5, the system control unit 11 substitutes the focal length of the imaging lens 1 for f in Equation (6), substitutes the focus lens position l1 for a in Equation (6), and solves for b. The focus lens position l1 is converted into the subject distance L1. Further, the system control unit 11 substitutes the focal length of the imaging lens 1 for f in Expression (6), substitutes the focus lens position l2 for a in Expression (6), and solves for b, whereby the focus lens position l2 is obtained. Is converted into the subject distance L2.

  After step S5, the system control unit 11 uses the subject distance L1 and the subject distance L2 to predict the subject distance L3 at the time of imaging the next frame of the N frames (step S6). A well-known method may be adopted as a method for predicting the subject distance. The system control unit 11 functions as a subject distance prediction unit.

  Next, the system control unit 11 converts the predicted subject distance L3 into the focus lens position l3. The system control unit 11 obtains the focus lens position l3 by substituting the subject distance L3 into b of Expression (6) (step S7).

  Next, the system control unit 11 acquires information on the maximum error (here, α) with respect to the focus lens position generated by the position phase difference AF processing unit 19 from the main memory 16 (step S8). The system control unit 11 functions as a maximum error information acquisition unit.

  Next, the system control unit 11 converts the value obtained by adding α to the focus lens position l3 into the subject distance L3a according to equation (6), and subtracts α from the focus lens position l3 according to equation (6). Conversion to the subject distance L3b (step S9).

  FIG. 7 is a diagram showing the relationship between the subject distance (b) and the focus lens position (image plane distance a) in the focused state.

  As shown in FIG. 7, when the subject distance is B, the focus lens position converted from the subject distance B is x1, and the subject distance Bb corresponding to the value obtained by adding α which is the maximum error to x1, and x1 The difference (absolute value ignoring the sign) between each of the subject distances Ba and the subject distance B corresponding to a value obtained by subtracting α, which is the maximum error, is a small value.

  On the other hand, when the subject distance is A that is sufficiently larger than B, the focus lens position converted from the subject distance A is x2, and the subject distance Ab corresponding to the value obtained by adding α that is the maximum error to x2, and The difference (absolute value ignoring the sign) between each of the subject distances Aa and the subject distance A corresponding to a value obtained by subtracting the maximum error α from x2 is a large value.

  In this way, when the subject distance predicted based on the plurality of focus lens positions generated by the phase difference AF processing unit 19 is large, the error with respect to the predicted distance also increases due to the maximum error with respect to the focus lens position. For this reason, if the focusing control is performed according to the predicted subject distance, the focusing accuracy is lowered.

  Therefore, the system control unit 11 determines whether or not the difference between the subject distance L3a and the subject distance L3b exceeds the threshold value TH in step S10, and if this difference exceeds the threshold value TH, the process proceeds to step S11. Processing is performed, and when this difference does not exceed the threshold value TH, processing in step S12 is performed.

  In step S11, the system control unit 11 predicts the focus lens position l3a at the time of imaging the next frame of the N frames from the focus lens positions l1 and l2. The system control unit 11 functions as a focus lens position prediction unit. As a method for predicting the focus lens position, a known method such as the method described in Patent Document 1 may be used.

  After step S11, the system control unit 11 performs focus control (first focus control) for moving the focus lens to the predicted focus lens position l3a (step S13).

  In step S12, the system control unit 11 performs focus control (second focus control) for moving the focus lens to the focus lens position l3 converted from the predicted subject distance L3.

  After step S12 and step S13, N is changed to (N + 1) in step S14, and the process of step S2 is performed.

  As described above, according to the digital camera of FIG. 1, only when the subject distance L3 predicted in step S6 is increased, the processing in steps S11 and S13 (the future focus lens position is determined from the plurality of past focus lens positions). Predictive focus control is performed). For this reason, compared with the conventional method in which the focus lens position is always predicted and focus control is performed, the amount of calculation required for moving object prediction can be reduced, and the follow-up speed for the moving object can be improved and the power consumption can be reduced. .

  In FIG. 6, as an error that may occur in the subject distance in the imaging of a frame to be performed in the future, first, the subject distance L3 is predicted, and the subject distance L3a and the subject distance L3b are generated from the subject distance L3 and the maximum error information. The difference between the subject distance L3a and the subject distance L3b is obtained as an error. Below, the modification of how to obtain | require this error is demonstrated.

  FIG. 8 is a flowchart for explaining a modification of a method for calculating an error that may occur in the subject distance. In FIG. 8, the same processes as those in FIG.

  After step S4, the system control unit 11 acquires information on the maximum error (here, α) with respect to the focus lens position generated by the phase difference AF processing unit 19 from the main memory 16 (step S20).

  Next, among the focus lens positions stored in the main memory 16, the system control unit 11 has the latest associated time (referred to as the focus lens position l1) and the next newest (focus lens position). From the main memory 16.

  Then, the system control unit 11 converts the value obtained by adding the maximum error α to the focus lens position 11 to the subject distance Ba, and converts the value obtained by subtracting the maximum error α from the focus lens position 11 to the subject distance Bb. Further, the system control unit 11 converts the value obtained by adding the maximum error α to the focus lens position l2 into the subject distance Aa, and converts the value obtained by subtracting the maximum error α from the focus lens position l2 into the subject distance Ab (step S21). ).

  By this processing, as shown in FIG. 9, two subject distances (black circles) are generated at time t1, and two subject distances (black circles) are generated at time t2.

  After step S21, the system control unit 11 uses the subject distance Ba and the subject distance Aa to predict the subject distance Ca that is the upper limit of the subject distance error at the imaging time t3 of the next frame (step S22. The system control unit 11 uses the subject distance Bb and the subject distance Ab to predict a subject distance Cb that is a lower limit error of the subject distance at time t3 (step S23).

  Next, the system control unit 11 determines whether or not the difference between the distance Ca and the distance Cb exceeds the threshold value TH. If the difference exceeds the threshold value TH, the process of step S11 is performed. When the difference does not exceed the threshold value TH, the process of step S5 in FIG. 6 and the process of step S6 in FIG. 6 are sequentially performed, and then the process of step S12 is performed.

According to the operation of FIG. 8, if the determination in step S24 is YES, step S1
2 to predict the subject distance L3 to be used. For this reason, unnecessary calculation can be reduced and power consumption can be reduced.

  So far, the description has been made on the assumption that the lens device is fixed to the camera body. However, the present invention can also be applied to an interchangeable lens digital camera in which a lens device can be attached to and detached from the camera body.

  In the case of an interchangeable lens digital camera, the system control unit 11 acquires information on the F value and focal length of the imaging lens included in the lens device from a storage unit built in the lens device. The system control unit 11 functions as an F value acquisition unit. Then, the system control unit 11 acquires information on the arrangement interval from the main memory 16 as a storage unit that stores information on the arrangement interval of the phase difference detection pixels, and this information and the F value acquired from the lens device. To calculate the maximum error and store it in the main memory 16. In addition, the system control unit 11 generates a function shown in Expression (6) from the focal length acquired from the lens apparatus and stores it in the main memory 16.

  Note that the F value and focal length information of the imaging lens in the interchangeable lens may be manually input to the system control unit 11 by the user.

  The system control unit 11 performs conversion processing from the focus lens position to the subject distance and conversion processing from the subject distance to the focus lens position according to the above functions stored in the main memory 16 in the operation flows shown in FIGS. Do. In step S9, the system control unit 11 uses the maximum error information stored in the main memory 16 to obtain the subject distances L3a and L3b.

  As described above, even in an interchangeable lens digital camera, the function and maximum error of Equation (6) are generated and stored in the memory in accordance with the lens device to be mounted, thereby tracking the moving object. Improvement of speed and reduction of power consumption can be realized.

  In the present specification, a digital camera is taken as an example of the imaging device, but an embodiment of a smartphone with a camera as the imaging device will be described below.

  FIG. 10 shows an appearance of a smartphone 200 that is an embodiment of the photographing apparatus of the present invention. A smartphone 200 shown in FIG. 10 has a flat housing 201, and a display input in which a display panel 202 as a display unit and an operation panel 203 as an input unit are integrated on one surface of the housing 201. Part 204 is provided. Such a housing 201 includes a speaker 205, a microphone 206, an operation unit 207, and a camera unit 208. Note that the configuration of the housing 201 is not limited thereto, and for example, a configuration in which the display unit and the input unit are independent can be employed, or a configuration having a folding structure and a slide mechanism can be employed.

  FIG. 11 is a block diagram showing the configuration of the smartphone 200 shown in FIG. As shown in FIG. 11, the main components of the smartphone include a wireless communication unit 210, a display input unit 204, a call unit 211, an operation unit 207, a camera unit 208, a storage unit 212, and an external input / output unit. 213, a GPS (Global Positioning System) receiving unit 214, a motion sensor unit 215, a power supply unit 216, and a main control unit 220. As a main function of the smartphone 200, a wireless communication function for performing mobile wireless communication via a base station device BS (not shown) and a mobile communication network NW (not shown) is provided.

  The radio communication unit 210 performs radio communication with the base station apparatus BS accommodated in the mobile communication network NW according to an instruction from the main control unit 220. Using this wireless communication, transmission and reception of various file data such as audio data and image data, e-mail data, and reception of Web data and streaming data are performed.

  The display input unit 204 controls the main control unit 220 to display images (still images and moving images), character information, and the like to visually transmit information to the user and to detect user operations on the displayed information. A so-called touch panel, which includes a display panel 202 and an operation panel 203.

  The display panel 202 uses an LCD (Liquid Crystal Display), an OELD (Organic Electro-Luminescence Display), or the like as a display device.

  The operation panel 203 is a device on which an image displayed on the display surface of the display panel 202 is placed so as to be visible, and detects one or a plurality of coordinates operated by a user's finger or stylus. When this device is operated with a user's finger or stylus, a detection signal generated due to the operation is output to the main control unit 220. Next, the main control unit 220 detects an operation position (coordinates) on the display panel 202 based on the received detection signal.

  As shown in FIG. 10, the display panel 202 and the operation panel 203 of the smartphone 200 exemplified as an embodiment of the photographing apparatus of the present invention integrally constitute a display input unit 204. The arrangement 203 covers the display panel 202 completely.

  When such an arrangement is adopted, the operation panel 203 may have a function of detecting a user operation even in an area outside the display panel 202. In other words, the operation panel 203 includes a detection area (hereinafter referred to as a display area) for an overlapping portion that overlaps the display panel 202 and a detection area (hereinafter, a non-display area) for an outer edge portion that does not overlap the other display panel 202. May be included).

  Note that the size of the display area and the size of the display panel 202 may be completely matched, but it is not always necessary to match them. In addition, the operation panel 203 may include two sensitive areas of the outer edge portion and the other inner portion. Further, the width of the outer edge portion is appropriately designed according to the size of the housing 201 and the like. Furthermore, examples of the position detection method employed in the operation panel 203 include a matrix switch method, a resistance film method, a surface acoustic wave method, an infrared method, an electromagnetic induction method, a capacitance method, and the like. You can also

  The call unit 211 includes a speaker 205 and a microphone 206, converts user's voice input through the microphone 206 into voice data that can be processed by the main control unit 220, and outputs the voice data to the main control unit 220. 210 or the audio data received by the external input / output unit 213 is decoded and output from the speaker 205. As shown in FIG. 10, for example, the speaker 205 can be mounted on the same surface as the surface on which the display input unit 204 is provided, and the microphone 206 can be mounted on the side surface of the housing 201.

  The operation unit 207 is a hardware key using a key switch or the like, and receives an instruction from the user. For example, as illustrated in FIG. 10, the operation unit 207 is mounted on the side surface of the housing 201 of the smartphone 200 and is turned on when pressed with a finger or the like, and turned off when the finger is released with a restoring force such as a spring. It is a push button type switch.

  The storage unit 212 includes a control program and control data of the main control unit 220, application software, address data that associates the name and telephone number of a communication partner, transmitted / received e-mail data, Web data downloaded by Web browsing, The downloaded content data is stored, and streaming data and the like are temporarily stored. The storage unit 212 includes an internal storage unit 217 built in the smartphone and an external storage unit 218 having a removable external memory slot. Each of the internal storage unit 217 and external storage unit 218 constituting the storage unit 212 includes a flash memory type, a hard disk type, a multimedia card micro type, and a multi-media card micro type. It is realized using a storage medium such as a card type memory (for example, MicroSD (registered trademark) memory), a RAM (Random Access Memory), a ROM (Read Only Memory) or the like.

  The external input / output unit 213 serves as an interface with all external devices connected to the smartphone 200, and communicates with other external devices (for example, universal serial bus (USB), IEEE 1394, etc.) or a network. (For example, the Internet, wireless LAN, Bluetooth (registered trademark), RFID (Radio Frequency Identification), Infrared Data Association (IrDA) (registered trademark), UWB (Ultra Wideband) (registered trademark) ZigBee) (registered trademark, etc.) for direct or indirect connection.

  As an external device connected to the smartphone 200, for example, a wired / wireless headset, a wired / wireless external charger, a wired / wireless data port, a memory card (Memory card) or SIM (Subscriber) connected via a card socket, for example. Identity Module Card (UIM) / User Identity Module Card (UIM) card, external audio / video equipment connected via audio / video I / O (Input / Output) terminal, external audio / video equipment connected wirelessly, existence / non-existence There are a wirelessly connected smartphone, a wired / wireless personal computer, a wired / wireless PDA, a wired / wireless personal computer, an earphone, and the like. The external input / output unit 213 transmits data received from such an external device to each component inside the smartphone 200, or allows the data inside the smartphone 200 to be transmitted to the external device. Can do.

  The GPS receiving unit 214 receives GPS signals transmitted from the GPS satellites ST1 to STn in accordance with instructions from the main control unit 220, executes positioning calculation processing based on the received GPS signals, and calculates the latitude of the smartphone 200. Detect the position consisting of longitude and altitude. When the GPS reception unit 214 can acquire position information from the wireless communication unit 210 or the external input / output unit 213 (for example, a wireless LAN), the GPS reception unit 214 can also detect the position using the position information.

  The motion sensor unit 215 includes a triaxial acceleration sensor, for example, and detects the physical movement of the smartphone 200 in accordance with an instruction from the main control unit 220. By detecting the physical movement of the smartphone 200, the moving direction and acceleration of the smartphone 200 are detected. The detection result is output to the main control unit 220.

  The power supply unit 216 supplies power stored in a battery (not shown) to each unit of the smartphone 200 in accordance with an instruction from the main control unit 220.

The main control unit 220 includes a microprocessor, operates according to a control program and control data stored in the storage unit 212, and controls each unit of the smartphone 200 in an integrated manner. In addition, the main control unit 220 includes a mobile communication control function that controls each unit of the communication system and an application processing function in order to perform voice communication and data communication through the wireless communication unit 210.

  The application processing function is realized by the main control unit 220 operating according to application software stored in the storage unit 212. Examples of the application processing function include an infrared communication function for controlling the external input / output unit 213 to perform data communication with the opposite device, an e-mail function for transmitting / receiving e-mails, and a web browsing function for browsing web pages. .

  Further, the main control unit 220 has an image processing function such as displaying video on the display input unit 204 based on image data (still image or moving image data) such as received data or downloaded streaming data. The image processing function is a function in which the main control unit 220 decodes the image data, performs image processing on the decoding result, and displays an image on the display input unit 204.

  Further, the main control unit 220 executes display control for the display panel 202 and operation detection control for detecting a user operation through the operation unit 207 and the operation panel 203. By executing the display control, the main control unit 220 displays an icon for starting application software, a software key such as a scroll bar, or a window for creating an e-mail. Note that the scroll bar refers to a software key for accepting an instruction to move the display portion of a large image that does not fit in the display area of the display panel 202.

  In addition, by executing the operation detection control, the main control unit 220 detects a user operation through the operation unit 207 or accepts an operation on the icon or an input of a character string in the input field of the window through the operation panel 203. Or a display image scroll request through a scroll bar.

  Further, by executing the operation detection control, the main control unit 220 causes the operation position with respect to the operation panel 203 to overlap with the display panel 202 (display area) or other outer edge part (non-display area) that does not overlap with the display panel 202. And a touch panel control function for controlling the sensitive area of the operation panel 203 and the display position of the software key.

  The main control unit 220 can also detect a gesture operation on the operation panel 203 and execute a preset function in accordance with the detected gesture operation. Gesture operation is not a conventional simple touch operation, but an operation that draws a trajectory with a finger or the like, designates a plurality of positions at the same time, or combines these to draw a trajectory for at least one of a plurality of positions. means.

  The camera unit 208 includes configurations other than the external memory control unit 20, the recording medium 21, the display control unit 22, the display unit 23, and the operation unit 14 in the digital camera shown in FIG.

  The captured image data generated by the camera unit 208 can be recorded in the storage unit 212 or output through the input / output unit 213 or the wireless communication unit 210.

  In the smartphone 200 illustrated in FIG. 10, the camera unit 208 is mounted on the same surface as the display input unit 204, but the mounting position of the camera unit 208 is not limited thereto, and may be mounted on the back surface of the display input unit 204. .

The camera unit 208 can be used for various functions of the smartphone 200. For example, an image acquired by the camera unit 208 can be displayed on the display panel 202, or the image of the camera unit 208 can be used as one of operation inputs of the operation panel 203.

  Further, when the GPS receiving unit 214 detects a position, the position can be detected with reference to an image from the camera unit 208. Furthermore, referring to the image from the camera unit 208, the optical axis direction of the camera unit 208 of the smartphone 200 is determined without using the triaxial acceleration sensor or in combination with the triaxial acceleration sensor. It is also possible to determine the current usage environment. Of course, the image from the camera unit 208 can also be used in the application software.

  In addition, the position information acquired by the GPS receiver 214 to the image data of the still image or the moving image, the voice information acquired by the microphone 206 (the text information may be converted into voice information by the main control unit or the like), Posture information and the like acquired by the motion sensor unit 215 can be added and recorded in the recording unit 212, or output through the input / output unit 213 and the wireless communication unit 210.

  Even in the smartphone 200 configured as described above, the solid-state imaging device 5 is used as the imaging device of the camera unit 208, and the main controller 220 performs the processing illustrated in FIGS. Can be improved.

  As described above, the following items are disclosed in this specification.

  The disclosed imaging apparatus is an imaging apparatus having an imaging element that images a subject through an imaging optical system including a focus lens, and the imaging element is a pair of light beams that have passed through different parts of the pupil region of the imaging optical system. A first signal detection unit that detects a signal corresponding to one of the pair of light beams and a second signal detection unit that detects a signal corresponding to the other of the pair of light beams, and drives the focus lens to A focus control unit that performs focusing control to focus on the image, and a correlation calculation between the detection signal of the first signal detection unit and the detection signal of the second signal detection unit obtained by imaging performed by the imaging device Based on the result, a focus lens position generation unit that obtains a focus lens position that is a position of the focus lens where an imaging surface on which a main subject is imaged and a light receiving surface of the image sensor coincide with each other The focus lens position obtained by the focus lens position generation unit is converted into a subject distance that is the distance between the main subject and the focus lens, and the time series generated by the subject distance conversion unit Generated from the subject distance corresponding to each of a plurality of consecutive imagings by a subject distance prediction unit that predicts a subject distance in imaging performed after the last imaging of the plurality of imagings, and the focus lens position generation unit A focus lens position prediction unit that predicts the focus lens position in imaging performed after the last imaging of the plurality of imaging from the focus lens position corresponding to each of a plurality of continuous imaging in time series, and For the focus lens position generated by the focus lens position generator A maximum error information acquisition unit that acquires large error information, and the focus control unit generates the focus control performed by the focus lens position generation unit as a focus control performed after the last imaging. And driving the focus lens according to the focus lens position predicted by the lens position prediction unit based on the focus lens position corresponding to each of a plurality of consecutively taken images in time series and the information on the maximum error. One of the focusing control and the second focusing control for driving the focus lens according to the subject distance predicted by the subject distance prediction unit is selected.

  In the disclosed imaging apparatus, the focus control unit determines a position obtained by adding and subtracting the maximum error to the focus lens position converted from the subject distance predicted by the subject distance prediction unit. When the difference between the two converted subject distances exceeds a threshold value, the first focusing control is selected. When the difference is equal to or less than the threshold value, the second distance is converted. Focus control is selected.

  In the disclosed imaging device, the focus control unit obtains the maximum error by adding the maximum error to the focus lens position corresponding to each of a plurality of time-series consecutive images generated by the focus lens position generation unit. From the position obtained by subtracting the maximum error from the focus lens position corresponding to each of the plurality of imaging, predicting the first subject distance in the imaging performed after the plurality of imaging, The second subject distance in the imaging performed next to the plurality of imaging is predicted, and the first focusing control is performed when the difference between the first subject distance and the second subject distance exceeds a threshold value. When the difference is less than or equal to the threshold value, the second focus control is selected.

  The disclosed image pickup apparatus is mounted with a storage unit that can exchange the image pickup optical system, and stores information on an arrangement interval of the first signal detection unit or the second signal detection unit in the image pickup device. An F value acquisition unit that acquires information on the F value of the imaging optical system, and the maximum error information acquisition unit is configured by the arrangement interval information stored in the storage unit and the F value acquisition unit. The maximum error information is acquired by calculating the maximum error from the acquired F value information.

  The disclosed focus control method is a focus control method in an image pickup apparatus having an image pickup device that picks up an image of a subject through an image pickup optical system including a focus lens, and the image pickup device has different pupil regions of the image pickup optical system. A first signal detection unit that detects a signal corresponding to one of the pair of light beams that has passed through the portion; and a second signal detection unit that detects a signal corresponding to the other of the pair of light beams. Based on the result of the correlation calculation of the detection signal of the first signal detection unit and the detection signal of the second signal detection unit obtained by the imaging performed by the imaging, the imaging plane on which the main subject is imaged and the imaging A focus lens position generation step for obtaining a focus lens position, which is the position of the focus lens that matches the light receiving surface of the element, and a focus lens position obtained in the focus lens position generation step. The subject distance conversion step for converting the sagged lens position into a subject distance that is the distance between the main subject and the focus lens, and the subject distance corresponding to each of a plurality of continuous imagings generated in the subject distance conversion step To a subject distance prediction step for predicting a subject distance in an imaging performed after the last imaging of the plurality of imaging, and a plurality of time-sequential imagings generated in the focus lens position generation step. A focus lens position predicting step for predicting the focus lens position in the imaging performed after the last imaging of the plurality of imaging from the focus lens position, and a maximum for the focus lens position generated in the focus lens position generating step Maximum error information acquisition process for acquiring error information And the focus lens position corresponding to each of a plurality of time-sequentially generated images generated in the focus lens position generation step as focusing control performed for the image capturing performed after the last image capturing. Based on the information on the maximum error, the first focus control for driving the focus lens according to the focus lens position predicted at the focus lens position prediction step, and the subject distance predicted at the subject distance prediction step. A focus control step of selecting any one of the second focus controls for driving the focus lens and executing the selected focus control before the imaging.

  The present invention is particularly convenient and effective when applied to digital cameras, smartphones, and the like.

DESCRIPTION OF SYMBOLS 1 Imaging lens 2 Aperture 5 Solid-state image sensor 11 System control part 19 Phase difference AF process part 52A, 52B Phase difference detection pixel

Claims (5)

An imaging apparatus having an imaging element that images a subject through an imaging optical system including a focus lens,
The image pickup device detects a signal corresponding to one of a pair of light beams that has passed through different parts of the pupil region of the image pickup optical system, and a signal corresponding to the other of the pair of light beams. A second signal detector that
A focus control unit that performs focus control to drive the focus lens to focus on a main subject;
An imaging plane on which a main subject is imaged based on a correlation calculation result of the detection signal of the first signal detection unit and the detection signal of the second signal detection unit obtained by imaging performed by the imaging device A focus lens position generation unit for obtaining a focus lens position that is a position of the focus lens at which a light receiving surface of the image sensor coincides with
A subject distance conversion unit that converts the focus lens position obtained by the focus lens position generation unit into a subject distance that is a distance between a main subject and the focus lens;
Subject distance prediction for predicting a subject distance in imaging performed next to the last imaging of the plurality of imaging from the subject distance corresponding to each of a plurality of continuous imagings generated in time series generated by the subject distance conversion unit And
Predicting the focus lens position in the imaging performed next to the last imaging of the plurality of imaging from the focus lens position corresponding to each of the plurality of time-sequential imagings generated by the focus lens position generation unit A focus lens position prediction unit to
A maximum error information acquisition unit that acquires information on the maximum error for the focus lens position generated by the focus lens position generation unit, and
The focus control unit converts the position obtained by adding and subtracting the maximum error from the focus lens position converted from the subject distance predicted by the subject distance prediction unit to the subject distance by the subject distance conversion unit, respectively. If the difference between the two converted subject distances exceeds a threshold value, the first focus control is selected as the focus control performed before the imaging performed after the last imaging, and the difference is When the threshold value is less than or equal to the threshold value, the second focus control is selected as the focus control performed before the imaging performed after the last imaging,
The first focusing control is a control for driving the focus lens according to the focus lens position predicted by the focus lens position prediction unit;
The second focusing control is an imaging apparatus which is a control for driving the focus lens in accordance with the subject distance predicted by the subject distance prediction unit . An imaging apparatus having an imaging element that images a subject through an imaging optical system including a focus lens,
The image pickup device detects a signal corresponding to one of a pair of light beams that has passed through different parts of the pupil region of the image pickup optical system, and a signal corresponding to the other of the pair of light beams. A second signal detector that
A focus control unit that performs focus control to drive the focus lens to focus on a main subject;
An imaging plane on which a main subject is imaged based on a correlation calculation result of the detection signal of the first signal detection unit and the detection signal of the second signal detection unit obtained by imaging performed by the imaging device A focus lens position generation unit for obtaining a focus lens position that is a position of the focus lens at which a light receiving surface of the image sensor coincides with
A subject distance conversion unit that converts the focus lens position obtained by the focus lens position generation unit into a subject distance that is a distance between a main subject and the focus lens;
Subject distance prediction for predicting a subject distance in imaging performed next to the last imaging of the plurality of imaging from the subject distance corresponding to each of a plurality of continuous imagings generated in time series generated by the subject distance conversion unit And
Predicting the focus lens position in the imaging performed next to the last imaging of the plurality of imaging from the focus lens position corresponding to each of the plurality of time-sequential imagings generated by the focus lens position generation unit A focus lens position prediction unit to
A maximum error information acquisition unit that acquires information on the maximum error for the focus lens position generated by the focus lens position generation unit, and
The focusing control unit is configured to add the plurality of maximum errors to the focus lens position corresponding to each of a plurality of time-series consecutive images generated by the focus lens position generation unit, and Predicting the first subject distance in imaging performed after imaging, and subtracting the maximum error from the focus lens position corresponding to each of the plurality of imaging, next to the plurality of imaging When the second subject distance in the imaging to be performed is predicted, and the difference between the first subject distance and the second subject distance exceeds a threshold value, Select the first focus control as the focus control, if the difference is less than or equal to the threshold, select the second focus control,
The first focusing control is a control for driving the focus lens according to the focus lens position predicted by the focus lens position prediction unit;
The second focusing control is an imaging apparatus which is a control for driving the focus lens in accordance with the subject distance predicted by the subject distance prediction unit . The imaging apparatus according to claim 1 or 2 ,
The imaging optical system is replaceable;
A storage unit for storing information on an arrangement interval of the first signal detection unit or the second signal detection unit in the imaging device;
An F value acquisition unit that acquires information on the F value of the mounted imaging optical system,
The maximum error information acquisition unit calculates the maximum error from the arrangement interval information stored in the storage unit and the F value information acquired by the F value acquisition unit, thereby calculating the maximum error information. An imaging device that acquires A focusing control method in an imaging apparatus having an imaging element that images a subject through an imaging optical system including a focus lens,
The image pickup device detects a signal corresponding to one of a pair of light beams that has passed through different parts of the pupil region of the image pickup optical system, and a signal corresponding to the other of the pair of light beams. A second signal detector that
A focus control step for driving the focus lens to perform focus control to focus on the main subject;
An imaging plane on which a main subject is imaged based on a correlation calculation result of the detection signal of the first signal detection unit and the detection signal of the second signal detection unit obtained by imaging performed by the imaging device A focus lens position generation step for obtaining a focus lens position that is a position of the focus lens at which a light receiving surface of the imaging element coincides,
A subject distance conversion step of converting the focus lens position obtained in the focus lens position generation step into a subject distance that is a distance between a main subject and the focus lens;
A subject distance prediction step for predicting a subject distance in an imaging performed after the last imaging of the plurality of imaging from the subject distance corresponding to each of a plurality of time-sequential imagings generated in the subject distance conversion step; When,
Predicting the focus lens position in the imaging performed next to the last imaging of the plurality of imaging from the focus lens position corresponding to each of the plurality of time-sequential imagings generated in the focus lens position generation step A focus lens position prediction step;
A maximum error information acquisition step for acquiring information on a maximum error with respect to the focus lens position generated in the focus lens position generation step ,
In the focus control step, a position obtained by adding and subtracting the maximum error to the focus lens position converted from the subject distance predicted in the subject distance prediction step is set as a subject distance by the subject distance conversion step, respectively. If the difference between the two converted subject distances exceeds a threshold value, the first focus control is selected as the focus control performed before the imaging performed after the last imaging, and the difference is When the threshold value is less than or equal to the threshold value, the second focus control is selected as the focus control performed before the imaging performed after the last imaging,
The first focusing control is a control for driving the focus lens according to the focus lens position predicted by the focus lens position prediction step;
The second focus control is a focus control method in which the focus lens is driven according to the subject distance predicted by the subject distance prediction step . A focusing control method in an imaging apparatus having an imaging element that images a subject through an imaging optical system including a focus lens,
The image pickup device detects a signal corresponding to one of a pair of light beams that has passed through different parts of the pupil region of the image pickup optical system, and a signal corresponding to the other of the pair of light beams. A second signal detector that
A focus control step for driving the focus lens to perform focus control to focus on the main subject;
An imaging plane on which a main subject is imaged based on a correlation calculation result of the detection signal of the first signal detection unit and the detection signal of the second signal detection unit obtained by imaging performed by the imaging device A focus lens position generation step for obtaining a focus lens position that is a position of the focus lens at which a light receiving surface of the imaging element coincides,
A subject distance conversion step of converting the focus lens position obtained in the focus lens position generation step into a subject distance that is a distance between a main subject and the focus lens;
A subject distance prediction step for predicting a subject distance in an imaging performed after the last imaging of the plurality of imaging from the subject distance corresponding to each of a plurality of time-sequential imagings generated in the subject distance conversion step; When,
Predicting the focus lens position in the imaging performed next to the last imaging of the plurality of imaging from the focus lens position corresponding to each of the plurality of time-sequential imagings generated in the focus lens position generation step A focus lens position prediction step;
A maximum error information acquisition step for acquiring information on a maximum error with respect to the focus lens position generated in the focus lens position generation step ,
In the focus control step, from the position obtained by adding the maximum error to the focus lens position corresponding to each of a plurality of time-series consecutive images generated by the focus lens position generation step, Predicting the first subject distance in imaging performed after imaging, and subtracting the maximum error from the focus lens position corresponding to each of the plurality of imaging, next to the plurality of imaging When the second subject distance in the imaging to be performed is predicted, and the difference between the first subject distance and the second subject distance exceeds a threshold value, Select the first focus control as the focus control, if the difference is less than or equal to the threshold, select the second focus control,
The first focusing control is a control for driving the focus lens according to the focus lens position predicted by the focus lens position prediction step;
The second focus control is a focus control method in which the focus lens is driven according to the subject distance predicted by the subject distance prediction step .

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